Thanks for your attention in advance,
I’ve met an issue with LINQ-2-SQL designer in VS 2008 SP1 which has made me CRAZY. I use Linq2sql as my DAL. It seems Linq2sql speeds up coding in the first step but lots of issues arise in feature specifically with table or object inheritance.
In this case I have a class Entity that all other entity classes generated by Linq2sql designer inherit from.
public abstract class Entity
{
public virtual Guid ID { get; protected set; }
}
public partial class User : monius.Data.Entity
{
}
And the following generated by L2S designer (DataModel.designer.cs)
[Column(Storage = "_ID", AutoSync = AutoSync.OnInsert, DbType = "UniqueIdentifier NOT NULL",
IsPrimaryKey = true, IsDbGenerated = true, UpdateCheck = UpdateCheck.Never)]
[DataMember(Order = 1)]
public System.Guid ID
{
get
{
return this._ID;
}
set
{
if ((this._ID != value))
{
this.OnIDChanging(value);
this.SendPropertyChanging();
this._ID = value;
this.SendPropertyChanged("ID");
this.OnIDChanged();
}
}
}
When I compile the code VS warns me that
Warning 1 'User.ID' hides inherited member 'Entity.ID'. To make the current member override that mplementation, add the override keyword. Otherwise add the new keyword.
That warning is obvious and I have to change the code generated by L2S designer (DataModel.designer.cs) to
[…]
public override System.Guid ID
{
…
protected set
…
}
And the code compiled with no error or warning and everyone is happy. But that is not the end of story.
As soon as I made changes to entities of the diagram (dbml) or even I open dbml file to view it, any change manually I made to designer has been vanished and POOF! Redo AGAIN. That is a painful job.
Now I wonder if there is a way to force L2S designer not changing portions of auto-generated code.
I’ll be appreciated if someone kindly helps me with this issue.
I suppose the questioner by now has overcome the issue. But I'll add an answer , for the benefiit of others who, like myself, googled their way to this post.
If you need to an override modifier on your linqToSql generated property;
1) open the dbml
2) right click and select properties on the Property you wish to add the override (or virtual, new or new virtual) keyword
3) change the Inheritance Modifier property to what you desire.
If all your base class does is:
public abstract class Entity
{
public virtual Guid ID { get; protected set; }
}
...then why not make it an interface instead?
Alternatively, you may want to look into using Damien Guard's T4 templates to customize the output of the code generator: http://l2st4.codeplex.com/
Related
Please tell me if this is a decent approach to deleting an Entity without fetching it given I have the ID.
I have a generic store with the following interface (I'll only show Delete):
public interface IStore : IReadOnlyStore
{
void Delete<TEntity>(TEntity entity) where TEntity : class, IEntity, new();
void SaveChanges();
}
And in the concrete Store class of that interface, here's my delete method:
public void Delete<TEntity>(TEntity entity) where TEntity : class, IEntity, new()
{
var obj = Ctx.Entry(entity);
if (obj.State == System.Data.EntityState.Detached)
{
Ctx.Set(typeof(TEntity)).Attach(obj.Entity);
}
Ctx.Set(typeof(TEntity)).Remove(obj.Entity);
}
I have tested both newing up an Entity:
Store.Delete(new Foo() { Id = request.Entity.Id });
as well as fetching an entity and then calling delete.
Through debugging, I have the desired affect on both scenarios.
I just want to make sure this is a good design and that there are no side effects to this approach.
For reference, Ctx is just the DbContext itself.
Thanks.
It's good design and doesn't have side effects :) (IMHO)
Two remarks:
I'm wondering if you could simplify your Delete method by:
public void Delete<TEntity>(TEntity entity)
where TEntity : class, IEntity, new()
{
Ctx.Entry(entity).State = EntityState.Deleted;
}
I would hope that setting the state to Deleted will attach automatically if the entity isn't already attached. But I am not sure if it works. (Let me know whether it works for attached and detached scenarios (if you should test this).)
If you have performance optimization in mind (avoiding to load the entities) don't forget that, if there are multiple entities to delete in the context, SaveChanges will still send one single DELETE statement per entity to the database. Bulk deletes with EF are quite terrible in performance and it's a terrain where going back to a SQL statements (DELETE ... WHERE ... IN ... many IDs....) sometimes makes sense (if performance matters).
I'm using EF 4.1 Code First. I have an entity defined with a property like this:
public class Publication
{
// other stuff
public virtual MailoutTemplate Template { get; set; }
}
I've configured this foreign key using fluent style like so:
modelBuilder.Entity<Publication>()
.HasOptional(p => p.Template)
.WithMany()
.Map(p => p.MapKey("MailoutTemplateID"));
I have an MVC form handler with some code in it that looks like this:
public void Handle(PublicationEditViewModel publicationEditViewModel)
{
Publication publication = Mapper.Map<PublicationEditViewModel, Publication>(publicationEditViewModel);
publication.Template = _mailoutTemplateRepository.Get(publicationEditViewModel.Template.Id);
if (publication.Id == 0)
{
_publicationRepository.Add(publication);
}
else
{
_publicationRepository.Update(publication);
}
_unitOfWork.Commit();
}
In this case, we're updating an existing Publication entity, so we're going through the else path. When the _unitOfWork.Commit() fires, an UPDATE is sent to the database that I can see in SQL Profiler and Intellitrace, but it does NOT include the MailoutTemplateID in the update.
What's the trick to get it to actually update the Template?
Repository Code:
public virtual void Update(TEntity entity)
{
_dataContext.Entry(entity).State = EntityState.Modified;
}
public virtual TEntity Get(int id)
{
return _dbSet.Find(id);
}
UnitOfWork Code:
public void Commit()
{
_dbContext.SaveChanges();
}
depends on your repository code. :) If you were setting publication.Template while Publication was being tracked by the context, I would expect it to work. When you are disconnected and then attach (with the scenario that you have a navigation property but no explicit FK property) I'm guessing the context just doesn't have enough info to work out the details when SaveChanges is called. I'd do some experiments. 1) do an integration test where you query the pub and keep it attached to the context, then add the template, then save. 2) stick a MailOutTemplateId property on the Publicaction class and see if it works. Not suggesting #2 as a solution, just as a way of groking the behavior. I"m tempted to do this experiment, but got some other work I need to do. ;)
I found a way to make it work. The reason why I didn't initially want to have to do a Get() (aside from the extra DB hit) was that then I couldn't do this bit of AutoMapper magic to get the values:
Publication publication = Mapper.Map<PublicationEditViewModel, Publication>(publicationEditViewModel);
However, I found another way to do the same thing that doesn't use a return value, so I updated my method like so and this works:
public void Handle(PublicationEditViewModel publicationEditViewModel)
{
Publication publication = _publicationRepository.Get(publicationEditViewModel.Id);
_mappingEngine.Map(publicationEditViewModel, publication);
// publication = Mapper.Map<PublicationEditViewModel, Publication>(publicationEditViewModel);
publication.Template = _mailoutTemplateRepository.Get(publicationEditViewModel.Template.Id);
if (publication.Id == 0)
{
_publicationRepository.Add(publication);
}
else
{
_publicationRepository.Update(publication);
}
_unitOfWork.Commit();
}
I'm injecting an IMappingEngine now into the class, and have wired it up via StructureMap like so:
For<IMappingEngine>().Use(() => Mapper.Engine);
For more on this, check out Jimmy's AutoMapper and IOC post.
I'm coming from a stored procedure and creating the data access layer manually approach. I am trying to understand where I should fit Linq To SQL or entity frameworks into my normal planning. I normally seperate out the business layer from the DAL layer and use a repository inbetween.
It seems that people will either use the generated classes from linq to sql, extend them by using the partial class or do a full seperation and map the generated linq classes to seperate business entities. I am partial to the seperate Business entities. However, this seems to be counterintuitive.
One of my last projects used DDD and the entity framework. When needing to udpate an object it moved the business entity to the repistory layer which when going to the DAL layer would create a context and than requery the object. It would than update the values and resbumit.
I didn't see the large point as the data context wasn't saved and required an extra query to grab the object before updating. Normally I would just do the update(If concurrency wasn't an issue)
So my questions come down to:
Does it make sense to seperate linq to sql generated classes into Business entities?
Should the data context be saved or is that impractical?
Thanks for your time, trying to make sure I understand. I normally like to seperate out as it makes it cleaner to understand even in some smaller porjects.
I currently hand roll my own Dto classes and Datacontext instead of using auto-generated code files from Linq to Sql. To give some background of my solution architecture/modeling, I have a "Contract" project, and a "Dal" project. (Also a "Model" project, but I'll try to stay focused here on Dal only). Hand-rolling my own Dtos and Datacontext, makes everything a lot smaller and simpler, I'll give a few examples of how I do that here.
I never return out a Dto object outside of the Dal, in fact I make sure to declare them as internal. The way I return them out is I cast them as an interface (interfaces are located in my "Contract" layer). We'll make a simple "PersonRepository" that implements an "IPersonRetriever and IPersonSaver" interfaces.
Contracts:
public interface IPersonRetriever
{
IPerson GetPersonById(Guid personId);
}
public interface IPersonSaver
{
void SavePerson(IPerson person);
}
Dal:
public class PersonRepository : IPersonSaver, IPersonRetriever
{
private string _connectionString;
public PersonRepository(string connectionString)
{
_connectionString = connectionString;
}
IPerson IPersonRetriever.GetPersonById(Guid id)
{
using (var dc = new PersonDataContext(_connectionString))
{
return dc.PersonDtos.FirstOrDefault(p => p.PersonId == id);
}
}
void IPersonSaver.SavePerson(IPerson person)
{
using (var dc = new PersonDataContext(_connectionString))
{
var personDto = new PersonDto
{
Id = person.Id,
FirstName = person.FirstName,
Age = person.Age
};
dc.PersonDtos.InsertOnSubmit(personDto);
dc.SubmitChanges();
}
}
}
PersonDataContext:
internal class PersonDataContext : System.Data.Linq.DataContext
{
static MappingSource _mappingSource = new AttributeMappingSource(); // necessary for pre-compiled linq queries in .Net 4.0+
internal PersonDataContext(string connectionString) : base(connectionString, _mappingSource) { }
internal Table<PersonDto> PersonDtos { get { return GetTable<PersonDto>(); } }
}
[Table(Name = "dbo.Persons")]
internal class PersonDto : IPerson
{
[Column(Name = "PersonIdentityId", IsPrimaryKey = true, IsDbGenerated = false)]
internal Guid Id { get; set; }
[Column]
internal string FirstName { get; set; }
[Column]
internal int Age { get; set; }
#region IPerson implementation
Guid IPerson.Id { get { return this.Id; } }
string IPerson.FirstName { get { return this.FirstName; } }
int IPerson.Age { get { return this.Age; } }
#endregion
}
You will need to add the "Column" attribute to all of your Dto properties, but if you notice, if there is a one-to-one correlation between what you want the field to be exposed as on the interface, and the name of the actual table column, you won't need to add any of the Named Parameters. In this example my PersonId in the database is stored as "PersonIdentityId", yet I only want my interface to make the field say "Id".
That's how I do my Dal layer, I believe this layer should be dumb, real dumb. Dumb in the sense that it is only there for CRUD (Create, Retrieve, Update and Delete) operations. All of the business logic would go into my "Model" project, which would consume and utilize the IPersonSaver and IPersonRetriever interfaces.
Hope this helps!
Hi I'm trying to create a basic data model / layer
The idea is to have:
Task task = TaskRepository.GetTask(2);
task.Description = "The task has changed";
task.Save();
Is this possible? I've tried the code below
Note: The TaskRepository.GetTask() methods detaches the Task entity.
I'd expect this to work, any ideas why it doesnt?
Thanks
public partial class Task
{
// Place custom code here.
public void Save()
{
using (TinyTaskDataContext db = new TinyTaskDataContext { Log = Console.Out })
{
db.Task.Attach(this);
db.SubmitChanges();
}
}
#region Metadata
// For more information about how to use the metadata class visit:
// http://www.plinqo.com/metadata.ashx
[CodeSmith.Data.Audit.Audit]
internal class Metadata
{
// WARNING: Only attributes inside of this class will be preserved.
public int TaskId { get; set; }
[Required]
public string Name { get; set; }
[Now(EntityState.New)]
[CodeSmith.Data.Audit.NotAudited]
public System.DateTime DateCreated { get; set; }
}
#endregion
}
Having done some reading I've realised I was implmenting the Repository pattern incorrectly. I should have been adding the Save method to the repository for conventions sake.
However, the actually problem I was having with regard to commiting the disconnected dataset was due to optimistic concurrency. The datacontext's job is to keep track of the state of it's entities. When entities become disconnected you loose that state.
I've found you need to add a timestamp field to the database table or I can set the UpdateCheck field on each column in my dbml file.
Here is some info about the UpdateCheck
Some useful links about disconnected Linq and plinqo
Great info on implementing the Repository pattern with LINQ
Short tutorial for implementing for updating and reattaching entities
Previously answer question
Rick Strahl on LINQ to SQL and attaching Entities
There is no need for this line (Task task = new Task();). The above should work although I've never seen it implemented in this manner. Have you thought about using the managers? Are you running into any runtime errors?
Thanks
-Blake Niemyjski
I'm building LINQ Models by hand, because I want to (understand what's reall happening).
There is a great light weight tutorial on turning standard classes into Linq Models I am reading Here.
For my sample application I have created some models that look like:
public class LoginModel
{
[Column(IsPrimaryKey=true,
DbType="UniqueIdentifier NOT NULL",
CanBeNull=false)]
public Guid LoginID { get; set; }
// .. and more question useless properties...
}
I'm definitely seeing a pattern for the primary key which led me to creating...
[AttributeUsage(AttributeTargets.Property
| AttributeTargets.Field,
AllowMultiple = false)]
public sealed class ColumnPrimaryKeyAttribute : DataAttribute
{
public ColumnPrimaryKeyAttribute()
{
CanBeNull = false;
IsPrimaryKey = true;
DbType = "UniqueIdentifier NOT NULL";
}
// etc, etc...
}
So when I use my new Attribute, LINQ is not picking up my attribute (even though it inherits from the same DataAttribute as Column. Is there a step I'm missing, or should I abandon this idea?
Try inheriting from ColumnAttribute...
public class ColumnPrimaryKeyAttribute : ColumnAttribute
Edit:
Never mind, I see that ColumnAttribute is sealed. You may be out of luck as my guess is LINQ is doing a System.Attribute.GetCustomAttributes(typeof(ColumnAttribute));